In recent years, needled nonwoven textile fabrics have become increasingly popular. Needled nonwovens are created by mechanically orienting and interlocking the fibers of a spunbond or carded web or batt. In particular, numerous needled or felted fabrics have been formed of either natural or synthetic fibers, or both; however, inorganic fibers such as glass fibers, are not normally suitable for felting or needling because glass fibers are quite brittle and do not lend themselves to being carded, needled, or felted. They are typically consolidated by either an air lay or wet lay process into a fabric having generally poor physical properties.
More recently, the desire to make thicker (1 inch or greater), lower weight basis, and lower density (less than about 5 pounds per cubic foot) insulating (thermal or acoustical) mats has created a renewed interest in needle punching of fiberglass fibers. In one process, e-glass fibers were opened, formed into a thick batt, and mechanically bonded on a needle loom in a single pass to form a mat. Unfortunately, these mats still have a density of 6 to 12 pounds per cubic foot.
Most recently, fiberglass fibers have been bonded together by resinous binders or thermoplastic adhesives to form thicker mats. Resinous binders, however, create undesirable problems with outgassing, and most contain either phenolic or melamine formaldehydes, which are environmentally and occupationally undesirable.